The present invention relates generally to cooling systems for electrical equipment. More particularly, the present invention relates to a unique angled mounting system for heat-generating electrical devices.
Electrical devices have found broad application in industrial systems. Such devices may be used in any system that provides or handles high levels of electricity, and may comprise anything from a simple resistor or fuse to a complex computer-controlled solid state device. Some electrical devices, such as Silicon Controlled Rectifiers (SCRs) produce a substantial amount of heat when they are in operation. In many cases, the heat level is minimal, but in some cases the heat produced causes degradation in the performance of the electrical devices that leads to measurable, and often valuable, losses.
The need often arises in power generation facilities to convert an alternating current (AC) of electricity into a direct current (DC) of electricity. For example, generator systems that provide AC electricity for industrial or consumer use typically require a source of DC electricity to excite the electromagnetic field of the main generator unit. This DC electricity is often provided by another AC generator, called an exciter, which may be mounted on the same shaft as the main generator unit. The AC output of the exciter must be converted into DC electricity before being introduced to the main generator unit. A device called a power bridge is often used to accomplish this AC to DC conversion, and power bridges are often comprised of a bank of SCRs.
SCRs are solid-state devices that provide flexible, reliable, and very fast control over voltages and currents. SCRs are silicon-based thyristor units, often having no moving parts, and which are typically shaped like a section of a cylinder or puck. Several SCRs (often six) may be arranged into a power bridge to provide AC-to-DC power conversion. The SCRs in a power bridge may be operated by sophisticated electronic systems that can be tailored to accommodate a great variety of electrical system hardware or power output requirements. Modern power generation systems rely very heavily on SCR-based power bridges to provide a reliable and consistent supply of electricity to consumers.
SCR power bridges are desirably arranged in a modular rack system. Rack-mounted SCRs are easily removed, repaired, replaced, or otherwise serviced, and the cost of constructing power systems is reduced by using modular rack assemblies. Furthermore, a rack-mounted system can be easily retrofitted with newer components, or such a system can be easily added to an existing power generation unit. Rack systems are also typically more compact than other SCR power bridges. Rack systems also provide a safety benefit in that the rack may be encased in a housing that prevents accidental contact with the electrical devices, and may be provided with lockout equipment that helps ensure that the power is off when the cabinet is opened.
As noted before, SCRs, like many other electrical components used in industrial applications, produce heat during their operation. The heat produced by SCRs may cause the SCRs or the surrounding equipment to fail or to operate at a reduced performance level. In order to prevent such overheating, the SCRs must be cooled. Prior art has proposed various methods for cooling SCRs. In a typical arrangement, the SCRs are encased in heat sinks comprising heat-conducting vanes. The heat sinks operate solely by free conduction of heat to the ambient air, or air may be forced over the vanes to provide additional convection cooling of the SCRs.
The overheating problem may be exacerbated when SCRs are placed in a modular rack mounting system. Many previously known rack systems mount the SCRs in a horizontal position. In another typical arrangement, the SCRs are mounted vertically on a flat surface or framework. In order to conserve space, the SCRs are usually mounted in columns having several SCRs mounted directly above or below one another.
Known SCR mounting systems, such as those discussed above, are problematic in that they fail to provide even cooling to all of the SCRs. Cooling air tends to rise through the rack, contacting several SCRs as it passes through the system. The air heats up as it rises, providing the upper SCRs less cooling benefit, and thereby reducing the performance of the upper SCRs.
Therefore, it would be desirable to provide an apparatus for holding electrical devices that provides consistent and even cooling of all of the electrical devices. It would also be desirable for such an apparatus to accommodate various sizes of electrical devices in a compact space. Furthermore, it would be desirable to provide an apparatus to hold electrical devices such that the electrical devices may be easily removed, repaired, replaced, or otherwise serviced.
The present invention overcomes the problems discussed above, and provides additional advantages, by employing an apparatus for mounting heat-generating electrical devices. The apparatus has a housing with a horizontal bottom, a horizontal top, and vertical sides extending vertically between the bottom and the top. Inside the housing are one or more heat-generating electrical devices, which are releasably mounted within the housing. The electrical devices are oriented at an angle relative to the bottom of the housing. In various embodiments of the invention, the mounting angle of the electrical devices may be selected to promote cooling, improve serviceability, provide a space-saving benefit, or to provide other benefits.
In one embodiment the electrical devices are three pairs of silicon controlled rectifiers. Each pair of silicon controlled rectifiers is mounted on an insulated mounting platform (xe2x80x9cplatformxe2x80x9d). Each is mounted in the housing at an angle, and the three platforms are arranged in a vertical stack. The housing also has ventilation openings in at least one of the bottom, top, and sides.
The present invention also consists of a method for mounting electrical devices in a housing such that the electrical devices are oriented at an angle relative to the bottom of the housing.